package org.sky.leetCode;

/**
 * @author fog
 * @description 反转列表
 * @date 2021/7/19
 */

public class ReverseList {

    static class ListNode {
        int val;
        ListNode next;

        public ListNode(int val, ListNode next) {
            this.val = val;
            this.next = next;
        }
    }

    /**
     * @param head -
     * @return null
     * @description 迭代法
     * @author fog
     * @date 2021/7/19
     */
    public static ListNode iterate(ListNode head) {

        ListNode prev = null, next;
        ListNode curr = head;

        while (curr != null) {
            next = curr.next;
            curr.next = prev;
            prev = curr;
            curr = next;
        }

        return prev;

    }

    public static void main(String[] args) {

        ListNode node5 = new ListNode(5, null);
        ListNode node4 = new ListNode(4, node5);
        ListNode node3 = new ListNode(3, node4);
        ListNode node2 = new ListNode(2, node3);
        ListNode node1 = new ListNode(1, node2);

        ListNode prev = iterate(node1);
        System.out.println(prev);

    }

}
